Yeah I've done this before, it's not very hard.
1. Cut & paste all the controls.
2. Create any methods on the new form that were on the old form.
3. Make sure that anywhere in the controls methods and form's methods that have THISFORM in it now point to the right places.

Generally I've found that having multiple page frames can actually backfire as opposed to have seperate forms when you're in a multi-developer enviornment because if one developer is working on something then another one can't be doing something else with it at the same time as you could if it was seperate forms - aaand of course it take take the initial form a little longer to load as it has to load all the controls / pageframes at the same time.
On the other hand I've found that users like it.

>Without knowing all the nuances and details, what do you think would be involved in taking 3 forms, all using the same class libraries for form and control classes, and turning them into tabs on a pageframe on 1 form? Looking for the high-level view here. Any easy way to do it? Just create a form with a pageframe on it and copy the entire group of form objects onto each page and deal with the fallout?